• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.05a
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• pp.140-143
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• 1992

This paper deals with the dielectric behaviors of $SF_{6}$ gas and prebreakdown growth caused by lightning impulse voltages in inhomogeneous field perturbed with a fixed needle-shaped protrusion on the electrode. The measuring interpretation of the external current induced by moving charges is described. The temporal growth of prebreakdown is obserbed by using a shunt and photomultiplier. The prebreakdown processes are initiated by the first streamer corona at a needle protrustion, the flashover of the main gap in the positive polarity is very sensitive to the local field and propagates into the gap with the leader mechanism. It is found that the dependence of the prebreakdown phenomena on the polarity of applied voltages is caused by the effect of space charges. In addition, the proposed measuring techniques are very useful to perform the measurements of avalanche currents, corona discharges in inhomogeneous fields ad partial discharges in voids.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.980-982
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• 1992

This paper deals with the dielectric behaviors of $SF_6$ gas and prebreakdown growth caused by lightning impulse voltages In inhomogeneous field perturbed with a fixed needle-shaped protrusion on the electrode. The measuring interpretation of the external current induced by moving charges is described. The temporal growth of prebreakdown is observed by using a shunt and photomultiplier. The prebreakdown processes are initiated by the first streamer corona at a needle protrusion, the flashover of the main gap in the positive polarity is very sensitive to the local field and propagates into the gap with the leader mechanism. It Is found that the dependence of the prebreakdown phenomena on the polarity of applied voltages is caused by the effect of space charges. In addition, the proposed measuring techniques are very useful to perform the measurements of avalanche currents, corona discharges in inhomogeneous fields and partial discharges in voids.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.137-141
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• 1996

This paper deals with the prebreakdown phenomena of $SF_{6}$ gap stressed by non-oscillating and oscillating impulse voltages in a strong inhomogeneous field disturbed by a fred needle shaped-protrusion on the earth-side electrode. The breakdown voltage-time characteristics were measured for both positive and negative polarities and over the gas pressure range of 0.1∼0.5 MPa, and the temporal developments of the 77breakdown were observed by a shunt of 50 n. The dependence of the leader stopping time on the gas pressure were obtained. The local field enhancement due to the space charges, which is produced by the streamer corona, has influence with the electrical breakdown of the test gap. The test streamer corona is oxy a necessary condition for the electrical breakdown and the subsequent ionization activities launch the leader at the local field region.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.05a
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• pp.204-207
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• 1995

This paper deals with the dielectric characteristics of $SF_{6}$ gas stressed by non-oscillating and oscillating impulse voltages in inhomogeneous field perturbed by a fixed needle shaped-protrusion. The breakdown voltage-time characteristics were measured for both polarities and over the gas pressure range from 0.1 to 0.5 [MPa], and the temporal developments of the prebreakdown were observed. The dependence of the leader stepping time on the gas pressure were obtained.

• Electrical & Electronic Materials
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• v.9 no.4
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• pp.385-395
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• 1996

이 논문은 금속성 돌기물에 의한 불평등전계중에서의 비진동성과 진동성 임펄스전압에 의한 SF$_{6}$ 가스의 절연파괴 특성에 대해 기술하였다. 절연파괴전압-시간특성을 가스압 0.1-0.5MPa의 범위에서 정.부 극성의 전압을 인가하여 측정하였으며, 그리고 50.ohm.분류기를 통해서 전구방전 전류를 관측하였다. 가스압력에 의한 리이더 진전시간의 의존성도 측정하였다. 스트리머 코로나에 의해 발생하는 공간전하에 의한 국부전계강화는 시험갭의 전기적 절연파괴에 영향을 미치는 것으로 판명되었다. 절연파괴는 초기 스트리머 코로나로부터 발단되어, 국부전계강화에 의한 리이더진전으로 이루어진다.

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.427-430
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• 1991

In this study, in order to observe treeing of prebreakdown phenomena, time variation of acoustic emission properties due to initiation and propagation of tree in LDPE was investigated under AC voltage. The experimental results were as following, pulse number and average amplitude of AE were increased along with near breakdown rather than tree initiation, also, according to increasing of applied voltage, tree propagation was blunted, while pulse number and average amplitude of AE was promoted. In each applied voltage, ${\phi}-a$ distributions during propagation of tree were changed to special patterns, skewness S and kurtosis K reflected well time variation of ${\phi}-a$ distribution patterns. It is thought that initiation and propagation state of tree can be easily monitored, so long as time variation of pulse number and average amplitude of AE, skewness Sand kurtosis K of ${\phi}-a$ distribution are always monitored.